Disinfection

Semmelweis demonstrated the value of handwashing with antiseptic solutions, when he obtained considerable reduction in the death rate from puerperal fever. Lister was also successful in reducing the number of wound infections by prophylactic application of an antiseptics (carbonic acid) to wounds. The importance of antiseptics and disinfectants has not diminished in this "golden age of antibiotics". Their uses range from control of communicable diseases to sterilization of sophisticated instruments, and treatment of fungal and bacterial infections of the skin and mucous membrane.

Definitions

Disinfectant: Usually a chemical agent that destroys disease causing pathogens or other harmful microorganisms, but might not kill bacterial spores.

Disinfection: Thermal and chemical destruction of pathogen and other types of microorganisms. Disinfection is less lethal than sterilization because it destroys most recognized pathogenic microorganisms but not necessarily all microbial forms (e.g. bacterial spores).

Sterilization: Validated process used to render a product free of all forms of viable microorganisms including bacterial spores.

Antiseptic: Substance that prevents or arrests the growth or action of micro-organisms by inhibiting their activity or by destroying them.

Asepsis: Prevention of contact with micro-organism.

Sanitizer: Agent that reduces the number of bacterial contaminants to safe levels as judged by public health requirements. Commonly used with substances applied to inanimate objects.

Sterile: State of being free from all living micro-organisms.

Hospital disinfectant: Disinfectant registered for use in hospitals, clinics, dental offices or any other medical related facility.

Germicide: Agent that destroys micro-organisms especially pathogenic organisms.

Detergent: Surface cleaning agent that makes no antimicrobial claims on the label. They comprise a hydrophilic component and a lipophilic component. It acts by lowering surface tension e.g. soap which removes bacteria along with dirt.

Deodorant: Deodorant is a substance which suppresses or neutralizes bad odors, e.g. lime and bleaching powder.

Properties of an ideal disinfectant

An ideal disinfectant fulfils the following criteria:

1. Broad spectrum: should have a wide antimicrobial spectrum.
2. Fast acting: should produce a rapid kill.
3. Not affected by environmental factors: should be active in the presence of organic matter (e.g., blood, sputum, feces) and compatible with soaps, detergents, and other chemicals encountered in use.
4. Nontoxic: should not be harmful to the user or patient.
5. Surface compatibility: should not corrode instruments and metallic surfaces, and should not cause the deterioration of cloth, rubber, plastics, and other materials.
6. Residual effect on treated surfaces: should leave an antimicrobial film on the treated surface.
7. Easy to use with clear label directions.
8. Odourless: should have a pleasant odour or no odour to facilitate its routine use.
9. Economical: should not be prohibitively high in cost.
10. Solubility: should be soluble in water.
11. Stability: should be stable in concentrate and use-dilution.
12. Cleaner: should have good cleaning properties.
13. Environmentally friendly: should not damage the environment on disposal.

Types of disinfection

A. Concurrent disinfection

It is the application of disinfective measures as soon as possible after the discharge of infectious material from the body of an infected person, or after the soiling of articles with such infectious discharges. In other words, the disease agent is destroyed as soon as it is released from the body , and in this way further spread of the agent is stopped. Concurrent disinfection consists of usually disinfection of urine, faeces, vomit, contaminated linen, clothes, hands, dressings, aprons, gloves, etc throughout the course of an illness.

B. Terminal disinfection

It is the application of disinfective measures after the patient has been removed by death or to a hospital or has ceased to be a source of infection or after other hospital isolation practices have been discontinued.

C. Precurrent (prophylactic) disinfection

Disinfection of water by chlorine, pasteurization of milk and handwashing may be cited as examples of precurrent disinfection.

Types of disinfection agents

The disinfective agents usually four types.

1. Natural agents: sunlight and air
2. Physical agents: burning, boiling, hot air, autoclaving and radiation.
3. Chemical agents: phenol, cresol, chlorhexidine, dettol, cetrimide, savlon, bleaching powder, chlorine tablets, iodine solution, ethyl and isopropyl alcohols, formaldehyde, potassium permanganate, hydrogen peroxide, paracetic acid, lime, ethylene oxide and heavy metals like silver etc.
4. Miscellaneous inactivating agents: pasteurization, microwave, ultraviolet radiation, ozone, and flushing and washer disinfectors.

Recommended disinfection procedures

1. Faeces and urine: usually disinfected by bleaching powder, crude phenol, cresol and by use of formalin.
2. Sputum: Burning, boiling, autoclaving and 5% cresol.
3. Room: Direct sunlight exposure, floors by chlorinated lime, formaldehyde solution 1% and cresol 2½ percent. When fumigation is required, the gas most commonly used is formaldehyde.